Develop and standardize methodology for the cryopreservation of sheathed and unsheathed microfilariae, particularly species of public health importance. The success of this study will be evaluated on the basis of the long-term storage and subsequent recovery of a high proportion of viable microfilariae, and the demonstration of viability by development of the microfilariae to the infective stage in an arthropod host. Also develop and standardize techniques for the cryopreservation of infective stage larvae, especially those of public health importance. The success of this study will be evaluated on the basis of the long-term storage and subsequent recovery of a high proportion of viable infective stage, and the demonstration that these larvae are viable by providing evidence that a microfilaremia can be produced in mammalian hosts.